Adrenal, thyroid, and rectal temperature responses of pinealectomized cockerels to different ambient temperatures

Pinealectomized (PX), sham-operated (PN), and control (C) cockerels were randomly assigned to three ambient temperatures (7, 23, or 37 C) at eight weeks of age. Rectal temperature (Tr) and blood were taken from birds either at mid-photophase or mid-scotophase (12L:12D) on five different days of the exposure period (0, 4, 8, 12, and 16 days). After 16 days of exposure to different ambient temperatures (Ta), birds were killed and their adrenal and thyroid glands removed. Serum T3 and T4 were measured by RIA in sera taken from PX and PN birds during both phases at each Ta. Pinealectomy depressed (P less than .05) somatic growth at each time measured independent of T3. A consistently lower Tr in PX birds held at 37 C produced an interaction (P less than .01) between pinealectomy and Ta. Across Ta, relative adrenal weights of PX cockerels (13.8 mg/100 g body weight were greater (P less than .05) than the PN and C average (12.7 mg/100 g body weight). There was an interaction (P less than .05) between pinealectomy and ambient temperature on thyroid weight; PX cockerels had smaller thyroids at 23 C and larger thyroids at 37 C than comparable controls. The PX cockerels had an average T3 concentration of 370.6 ng/100 ml compared to 350.5 ng/100 ml for PN birds. The hot environment (37 C) markedly depressed (P less than .01) serum T3 concentrations independent of surgical treatment. In PX cockerels, decreased body weights, lower Tr, and general adrenal enlargement indicate that the avian pineal gland is involved in endocrine function and maintenance of body temperature as well as normal somatic growth.